The American economy has traditionally been divided into three sectors: government, for-profit businesses and non-profit charities. In more recent years, students of American business have begun talking about a fourth category, often called the "for-benefit" sector. Fitting in between traditional businesses and charitable groups, for-benefit organizations are moneymaking enterprises with a social agenda. American universities are beginning to recognize this fourth sector of the economy, and to prepare students to enter it.

Custom Packaging of Lebanon, Tennessee, makes cardboard sales displays used in grocery stores and movie theaters. The company recently hired sustainability consultant William Paddock to help them "green" their operations. Paddock showed them how to generate less waste and recycle what trash they did produce. He also convinced the company to install one of the area's largest solar array on the factory roof, reducing their carbon footprint.

Paddock says there are many motivations for being socially responsible.

"For us it's about protecting the environment, being better to society, but also there's an economic piece to it," said Paddock. "We love to, you know, find our passions, but also save somebody money."

Paddock's been helping companies save money with green solutions for about ten years, but recently added a little green to his own resume. Last year, he completed an advanced degree in business administration from nearby Lipscomb University; a degree that included a strong emphasis on environmental sustainability. Paddock says the classes improved his ability to connect with his customers.

"The biggest benefit of going through a program like that is to learn how to talk about a subject like sustainability," added Paddock. "How do you convince a business that looking at their carbon emissions is actually a viable business option?"

Belmont University, in Nashville, takes a different approach for those interested in a for-benefit career. These students will be among the first to graduate with the university's new bachelor's degree in Social Entrepreneurship. Today, they are arranging senior internships with local charities.

Bernard Turner, director of Belmont's Center for Social Entrepreneurship, says American universities were slow to offer degrees in for-benefit fields of study, and are now being forced to quickly add those programs.

"Students are saying, 'Now I want to be an entrepreneur, but I want to do something that deals with a social problem or a social issue that's dear to me.' So what has happened is that a lot of these programs have come to fruition because they are student-driven; student desires about this," noted Turner.

Students are driven by very personal motivations.

"We've even had students that said, you know, 'Alcoholism was an issue in my family. So how can I study social entrepreneurship and do something about giving these folks a second chance when they come out of treatment?'" added Turner.

Andrew Bishop is one of the program's star students. He launched his first charity when he was still in high school. Turner is helping him launch a second charity that connects professors with opportunities to volunteer in the community.

Bishop says he and his peers are motivated by what they see in the media.

"Even 20 years ago, you really only knew what was going on in your community," said Bishop. "But now, you have this world and worldwide sense of what's going on and I think it's challenged young people as they're growing up to kind of look at 'How can I make a difference and how can I solve some of these world issues with what I do with my career?'"

That growing desire to make a difference and a living at the same time, is why Bishop says American universities are likely to continue expanding their degree offerings in socially-centered areas of study.

"I think more people want to be able to say that when they retire, 'I did make a difference in my work, and I did make a difference in the life of someone else through what I did each and every day,'" added Bishop.

From just a handful of offerings 20 years ago, there are now more than 60 American universities offering "green" business degrees.